Biosynthesis of the first enediyne core intermediate by PKSE and TE. (A) Formation of the identical polyene product (●) using sgcE/E10 coexpression in E.coli (I) or ncsE/E10 in E.coli (II), S. lividans (III), or S. albus (IV). (B) UV/Vis profile of 1,3,5,7,9,11,13-pentadecaheptaene (1). (C) Final domain assignments and activity of nine-membered enediyne PKSE. (D) Tandem reactions catalyzed by PKSE/TE to produce the linear heptaene 1, the first isolable intermediate toward the biosynthesis of the enediyne core. The last intermediate bound to the ACP is a hypothetical PKS product.